Re: [RFC][PATCH 0/2] Avoiding DWC3 transfer stalls/hangs when using adb over f_fs

[John Stultz]

On Thu, Jan 23, 2020 at 9:31 AM Felipe Balbi <balbi@xxxxxxxxxx> wrote:
> "Yang, Fei" <fei.yang@xxxxxxxxx> writes:
> >>> Hey all,
> >>>    I wanted to send these out for comment and thoughts.
> >>>
> >>> Since ~4.20, when the functionfs gadget enabled scatter-gather
> >>> support, we have seen problems with adb connections stalling and
> >>> stopping to function on hardware with dwc3 usb controllers.
> >>> Specifically, HiKey960, Dragonboard 845c, and Pixel3 devices.
> >>
> >> Any chance this:
> >>
> >> https://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb.git/commit/?h=testing/next&id=f63333e8e4fd63d8d8ae83b89d2c38cf21d64801
> > This is a different issue. I have tried initializing num_sgs when debugging this adb stall problem, but it didn't help.
>
> So multiple folks have run through this problem, but not *one* has
> tracepoints collected from the issue? C'mon guys. Can someone, please,
> collect tracepoints so we can figure out what's actually going on?

Sure, I can do that. Though to be fair, I recall Fei sending out
tracepoint data earlier that didn't get a response.

So attached is trace/regdump data for db845c both in the failure case
and with the patch ("Correct the logic for finding last SG entry").

I'll collect HiKey960 data here after lunch when I can swap over to
that board and will send it along soon.

Thanks so much for taking a look at this!
-john

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